Disc brake actuating and adjusting mechanism



Aug. 7, 1962 Original Filed Nov. 10, 1958 0. K. KELLEY ET AL 3,048,241

DISC BRAKE ACTUATING AND ADJUSTING MECHANISM 5 Sheets-Sheet 1 INVENTORSOliver K. Kelley BY Gilbert K. House Fig. b. 2A"

Their A fforne Aug. 7, 1962 0. K. KELLEY ETAL DISC BRAKE ACTUATING ANDADJUSTING MECHANISM 5 Sheets-Sheet 2 Original Filed Nov. 10, 1958INVENTORS Oliver K. Kelley y Gilbert K. House Their Affornezs 1962 0. K.KELLEY ETAL 3,048,241

DISC BRAKE ACTUATING AND ADJUSTING MECHANISM Original Filed Nov. 10,1958 5 Sheets-Sheet 3 INVENTORS Oliver K. Kelley Fl 7 By Gilbert K.Hause Their Aftorne Aug. 7, 1962 0. K. KELLEY ETAL DISC BRAKE ACTUATINGAND ADJUSTING MECHANISM Original Filed Nov. 10, 1958 5 Sheets-Sheet 4INVENTORS er K. Kelley er? K.

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Ollv BY Gilb Hausa Their Aflom TIIII,

Aug. 7, 1962 0. K. KELLEY ET AL DISC BRAKE ACTUATING AND ADJUSTINGMECHANISM 5 Sheets-Sheet 5 INVENTORS Oliver K. Kelley By Gilbert K.House Original Filed Nov. 10, 1958 The! r Attorney United States Thisinvention relates to a vehicle disk brake and more particularly to aparking brake actuating mechanism for a vehicle disk brake.

This is a divisional application of the patent application S.N. 772,977,filed Nov. 1958, now Patent Number 2,995,215, issued August 8, 1961.

One of the problems of operating a parking brake in conjunction with -avehicle disk brake has been in providing a parking brake which providesadequate braking after the friction disks have cooled. If the brakedisks have been in operation for a considerable time prior toapplication of the parking brake, they have a certain amount of axialexpansion due to the heating of the brake disks. With the closetolerances employed between the friction disks, the changing from a hotto a cool temperature is sometimes sufiicient to release the brakingeffect provided by the parking brake.

It has been difficult to provide a braking mechanism within the limitedspace usually present in a vehicle disk type of brake. The parking brakemust operate within this limited space and yet provide adequate brakingunder all conditions.

It is an object of this invention to provide a parking brake whichoperates in conjunction with a hydraulically operated vehicle diskbrake.

It is another object of this invention to provide a par ing brake with asufficiently high mechanical advantage to give suflicient axialcompression of the disk stack in a vehicle disk brake to provideadequate braking under all conditions.

It is a further object of this invention to provide a ball groove nutand ball groove sleeve which is cable operated to provide axialelongation for the actuation of a parking brake operating in conjunctionwith a vehicle disk brake.

It is a further object of this invention to provide a cable operatedball groove nut and ball groove sleeve mechanism for axial elongationand operation of a vehicle disk 'brake. In conjunction with this type ofparking brake, it is further intended that this type of mechanism shouldoperate with a hydraulic annular piston which is used for actuation ofthe regular breaking means.

It is a further object to provide a means for adjusting the clearancebetween the brake disks automatically during the braking cycle. Thisautomatic adjustment is provided by movable members which have a closefitting tolerance with the annular hydraulic piston where they arefitted into the piston.

These objects are accomplished by a vehicle parking brake actuatingmechanism which operates in conjunction with the vehicle disk brake. Thevehicle disk brake is actuated by an annular hydraulic piston. Thishydraulic piston operates as a ball groove sleeve when actuated by theparking brake mechanism. A ball groove nut is placed concentrically withthe annular piston with a mating helical ball groove which is cutpartially within the nut and partially in the piston sleeve. The ballgroove nut is rotated by means of a cable. Spherical balls are insertedin the helical ball groove and resiliently held in position by springs.As the ball groove nut is rotated in relation to the ball groove pistonsleeve, the two members elongate axially in relation to each atent iceother. These two members being combined in an enclosure with the pistonsleeve abutting the braking disks, and the brakes are actuated when themechanism is elongated.

To give added assistance to the actuation of the parking brake, thehydraulic brakes may also be actuated and thereby providing greatercompression of the brake disk stack. With the added pressure created onthe disk stack, the releasing of the brakes upon cooling of the brakedisks is quite unlikely.

An added feature is incorporated in this braking structure whereby anautomatic clearance adjustment is built into the braking mechanism. Thisclearance is provided by a closely fitted member projecting into theannular piston. The member moves through a flange in the piston duringbrake actuation and has a clearance between the housing and the memberequal to the clearance between the brake disks. The retraction springsreturn the piston so the member rests on the housing. The member slidesthrough the annular piston at a rate equal to the wear on the diskstacks.

Further objects and advantages of the present invention will be apparentfrom the following description, reference being had to the accompanyingdrawings wherein a preferred embodiment of the present invention isclearly shown.

F IG. 1 is a cross-section view of the vehicle disk brake in a verticalplane through the center line of the wheel axle. This view also shows aparking brake actuating means.

FIG. 2 is a cross-section view taken on line 22 of FIG. 1. This viewshows the end portion of the parking brake actuating means and the cableconnection.

FIG. 3 is a cross-section view taken on line 33 of FIG. 1. This viewshows a central portion of the parking brake actuating means and themeans for retaining the spherical balls. A portion of the view is cutaway for clarification of the parts.

FIG. 4 is a cross-section view taken on line 44 of FIG. 3.

FIG. 5 is a cross-section view taken on line 5-5 of FIG. 3.

FIG. 6 is a cross-section View taken on line 6-6 of FIG. 2.

FiG. 7 is a cross-section view of a modified version of the vehicle diskbrake and parking brake actuating mechanism. The view is taken on aplane vertically through the center line of the wheel shaft.

FIG. 8 is a cross-section view taken on line 88 of FIG. 7 showing themounting of the cable, and the spherical ball members between the ballgroove nut and the ball groove sleeve member.

FIG. 9 is a cross-section view of another modification of the emergencybrake actuating means.

FiG. 10 is a cross-section view taken on line 1010 of FIG. 9.

FIG. 11 is a cross-section view taken on line 11--11 of FIG. 9.

FIG. 1 illustrates the braking structure and the parking brake actuatingmeans. The cross-section of the wheel is shown at l which is bolted tothe wheel hub 2 by means of bolts 3 and nuts 6. An integral flange ofthe wheel shaft 7 is aligned by means of the dowel pins 4- and connectedto the hub portion 2 by means of bolts 5. The wheel shaft 7 extendsthrough the internal portion of the brake structure and the parkingbrake actuating means. The hub section 2 forms a housing around theouter periphery of the brake disks. A seal 8 is provided between the hub2 and the flange of shaft 7. The rotating disks 9 are mounted on aspline connection on the internal periphery of the hub 2. The rotatingdisks 9 are alternately spaced between stator disks 10. The

stator disks 1%) are mounted on the outer periphery of the shaft housing11 by means of a spline connection. The rotating disks 9 carry afriction material which engages the stator disks 1t Inboard of thebraking disks 9 and 10 is mounted a backing plate 12. On the outboardside of the braking disks 9 and 10 is mounted a pressure plate 13.

A ball bearing assembly 16 is mounted on the inner periphery of the hubsection 2 inboard of the backing plate 12. This ball bearing assembly 16comprises an outer race 14a, an inner race 14, a ball bearing cage 15and rolling element 15a. A seal 17 is provided on the inner periphery ofthe ball bearing assembly 16. A seal 18 is provided on the outerperiphery of the ball bearing assembly 16 and the inner periphery of thehub 2. An internal seal is pro ided at 19 between the outer race 14a andthe inner race 14. The inboard side of the ball bearing assembly 16abuts the housing 11 and also a retainer ring 20 which is mounted on theinboard edge of hub 2.

The housing 11 is connected to a shaft housing extension 21 by means ofbolts 22. This housing extension 21 extends inward to the difiierentialof the vehicle. Within the housing extension 21 is mounted the parkingbrake actuating means. A sleeve member 23 is placed about the driveshaft 7 and extends from a point within the housing extension 21 to theoutboard side of the pressure plate 13. This sleeve member 23 has aradical flange 23a on its outboard end which actuates the disk stackwhen the sleeve is moved axially inward. The inboard end of this sleevereceives a snap ring 24 in a groove about its outer periphery. This snapring 24 abuts the inboard side of the annular wheel piston 25. A seal 26is provided between the inboard end of the annular fluid piston and theinternal periphery of the housing extension 21. The outboard side of thewheel piston 25 is provided with two seals 27 and 28 which provide apressure chamber for actuating of the disk brake. An inlet fluid passage29 is provided for the actuating fluid. This passage is connected to aduct 30 which extends to the master cylinder which is operated by thebrake pedal 31.

About the outer periphery of the annular piston 25 is cut a helical ballgroove. This groove has a mating section on the ball groove nut 32. Thisgroove receives spherical balls which move the annular piston axially inrelation to the ball groove nut 32 as the ball groove nut is rotated.The ball groove nut 32 is provided with an annular groove 33 forreceiving spherical balls 34. These balls fit into a mating groove 35which is on the inboard side of the shaft housing 11.

The shaft housing 11 is held in non-rotative alignment with the annularwheel piston 25 by means of alignment dowels 36. These dowels 36 arespaced at intervals around the radical flange of housing 11 within thefluid operating chamber extending into the annular fluid piston.

The shaft housing extension 21 has a ball hearing assembly 37 insertedwithin its inner periphery for receiving the shaft member 7. A seal 33is provided on the ball bearing assemblys outer periphery and a seal 39is disposed on the inner periphery of the bearing assembly. A fluid seal40 is provided between the inner and outer races of the ball bearingassembly 37. This ball bearing assembly abuts a radical flange portionon the inner periphery of the shaft housing extension 21. A returnspring 41 is placed between the ball bearing assembly 37 and the annularpiston 25.

The means for providing the proper clearance between the rotating andstationary disks is shown in FIG. 1. The screw member 42 is threadedlyengaged in the shaft housing 11. The shoulder portion 43 abuts againstthe radical flange of the inboard side of the housing extension 11. Thedistance between this shoulder 43 and the head 44 of the screw member 42is a predetermined length. The sleeve member 45 is placed on the screwmember 42 prior to assembling. The difference in length of the sleevemember 45 and the distance between the shoulder 43 and the head 44 isthe predetermined clearance to be provided between the braking disks.The sleeve 45 has a close fitting tolerance on the inner periphery ofthe hole 46 of the fluid piston 25 in which it is inserted.

FIG. 2 is a cross-section view showing the end portion of the parkingbrake actuating means. The housing extension 21 is mountedconcentrically around the ball groove nut 32. The extension housing 21is also shown extending within the ball groove nut 32. A coil spring 50is located concentrically within these two portions of the shaft housingextension 21. The one end of spring 50 has a radially extending portion51 which engages a portion of the ball groove nut 32. The opposite endof this coil spring extends axially outboard into the annular wheelpiston 25. This end of the spring 52 is shown inserted in a hole of theannular piston 25 by FIG. 6.

The actuating sleeve 23 is shown concentrically mounted about the wheelshaft 7. The cable 53 is connected to axially extending flanges 54 and55. The cable 53 is wound around the flange 54 and then doubled backbetween the two similarly shaped flanges on the ball groove nut 32. Thiscable wraps around the outer periphery of the ball groove nut 32 andextends outward through a cable fitting of the shaft housing extension21.

The cable fitting comprises a sleeve 56 which is inserted in the shafthousing extension 21. Within the inner periphery of the sleeve 56 ismounted a cable guide 57 which has a seal member 58 about its outerperiphery and the inner periphery of the sleeve 56. The cable guide 57is held in position by means of a threaded sleeve which engages theinner periphery of the outer end of sleeve 56. The cable 53 extends intoan armoured portion 59 on the outer side of the cable fitting. About theouter periphery of the armoured portion 59 a spring is provided which isalso shown at 60.

FIG. 3 is a cross-section view of the cable actuated parking brakemechanism. This view illustrates the mounting of the spherical balls 61within the mating ball grooves. A pin 62 is mounted on the hydraulicpiston 25 adjacent the end of the spherical balls '61. The pin 63 ismounted in the ball groove nut '32 adjacent the spring 64. This springextends from the pin 63 in the annular ball groove to the adjacent endof the spherical balls 61. The mounting of the pin 62 is also shown inFIG. 4. The groove 33 in the ball groove nut 32 is also shown in FIG. 4.This groove receives the spherical ball 34.

FIG. 7 is a modified version of the parking brake actuating mechanism.The hub or wheel mounting flange is shown at 70 as an integral part ofthe shaft 71. The shaft 71 is rotatably mounted within the brake housing72 which receives the ball bearing assembly 73. The ball bearingassembly 73 is retained in position by the annular flange member 74which is held in place by the bolts 75. A seal member 76 is placed onthe outer periphery of the ball bearing assembly 73. A second seal 77 isalso placed on the inner periphery of the ball bearing assembly 73. Thebrake housing 72 is mounted adjacent to the wheel cylinder 78 and heldin position by bolts 79. A seal 86 is provided between the brake housing72 and wheel cylinder 78. On the inboard side of the wheel cylinder 78,a shaft housing 81 is bolted by means of bolts =82. The ball bearingassembly 83 is inserted within shaft housing 81. A seal member 84 isplaced between the shaft 71 and the ball bearing assembly 83. A seal 85is placed between the shaft housing 81 and the ball bearing assembly 83.A seal 86 is also placed between the inner and outer races of the ballbearing assembly 83.

The modification of the brake assembly employs an annular piston whichmoves axially outboard to actuate the brakes. The brake housing 72operates as the pressure plate for the disk stack. The rotating disks'87 are mounted on a spline portion of shaft 71. These rotating disks 37are provided with a friction material for engaging the stator disks 88.The stator disks =88 are mounted on pins 89 which fit into aligned holesin the brake housing 72 and the wheel cylinder 78. A seal 90 is providedbetween the brake housing 72 and the wheel cylinder 78. The fluidactuating chamber for the hydraulic annular piston is shown at 91. Theseal 92 at the outboard end and the seal 93 at the inboard end confinethe fluid within the actuating chamber 91.

The annular piston 191 is held in a nonrotating position by means of thepin 89. These pins 89 are spaced about the outboard side of the wheelcylinder 73. Alternately spaced between these pins 89 are the clearanceadjusting devices. These devices comprise pins 94 which are mounted inclosely fitted holes in the radially outer portion of the annular piston191. As the braking disks become worn, the annular piston 191 ispermitted to move a greater distance outboard and the pins 94 are movedwithin the annular piston. The movement of the pins M is in a directrelation to the wear of the brake disks. The annular piston 191 isreturned to its normal position upon release of the brakes by the returnsprings 95. The inboard end of the pins 94 determine the retractedposition of the piston 191.

The annular piston has a helical ball groove about its inner peripheryon the inboard end. A ball groove nut 96 has a mating ball groove aboutits outer periphery on its outboard end. Spherical balls 97 are placedwithin the mating portions of the ball groove portion of the fluidpiston and the ball groove portion of the nut @6. As the ball groove nut96 is rotated, a pressure is created on the groove 98 on the inboardside of nut 96. The groove 93 has a mating portion on the annularshoulder member 9% for receiving spherical balls 1%. Upon rotation ofthe ball groove nut 96 the annular piston is moved axially outboard bythe force created on the spherical balls 97 within their helical groove.The outboard axial movement of the piston 191 creates engagement of thebraking disks.

FIGURE 8 illustrates a cross-section portion of the parking brakeactuating means. The wheel cylinder 78 with its attaching bolts 79 isshown around the outer periphery of the rotating portion of the brakemechanism. The wheel cylinder 78 encloses the rotating mechanism andprovides a seating portion for the annular shoulder member 99 with anannular groove for receiving the balls 1%. The spherical balls 1% areplaced between the ball groove nut 96 and the annular shoulder 99. Theannular shoulder member $9 is in a non-rotating position on the wheelcylinder 78. The ball groove nut 96 is rotatably mounted on thespherical balls 97. The cable 185 extends inward within the housing andis attached to a ball 1% which is fitted into a slot 1tl7 in the ballgroove nut as. The cable 1% extends outward from the housing portionthrough a cable guide 108.

The cable guide 168 is fixed in position by means of a pin 199 and isprovided with a seal 11% on its inner end. The outer end of the cableguide is received within an extended portion of the cable guide 111which carries an armored portion 112 about its inner periphery. Thecable 105 extends outwardly where it is attached to a handle member 113which is used for actuating the parking brake mechanism. The handlemember 113 is provided with a ratchet portion 114 which engages the pawl115 which locks the ratchet arm 114 upon actuation of the brakingmechanism.

FIGS. 9, l0, and 11 illustrate a modification of the parking brakemechanism. FIG. 9 is taken through the center line of the wheel shaft ina vertical plane. The wheel cylinder 116 is shown connected to the shafthousing 117 by means of bolts 118 and washers 119. A seal 120 is shownbetween the wheel cylinder 116 and shaft housing 117. The shaft 121 isrotatably mounted within the ball bearing assembly 122 which is mountedon the inner periphery of the shaft housing 117. A fluid seal assembly124 is mounted adjacent the ball bearing assembly. The annular wheelpiston 125 is mounted within the wheel cylinder 116. A needle bearingassembly 126 is mounted axially inboard from the annular piston 125.This needle bearing assembly 126 is mounted adjacent the ball groove nut127 which has a helical ball groove on its inner periphery. A ballgroove sleeve 12% is mounted within the inner periphery of the ballgroove nut 127 and has a mating helical ball groove on its outerperiphery. Spherical balls are retained within the mating portion of thehelical ball groove nut 127 and ball groove sleeve 12%.

A cable 138 is wrapped around the outer periphery of the ball groove nut127. On the inboard side of the ball groove nut 127 is mounted aresilient spring 132 for returning the brake actuating means after themechanism has been released. A pin 131 is mounted within housing 116 andfunctions as a stop means which abuts against the one end of the returnspring 132 mounted within the housing 116 and abutting the pin 131. Thespring 132 extends about the inner periphery of the housing 116 to whereit abuts two pins 133 and 134 at the opposite end of spring 132. It willbe noted that the flange portion 135 which is a portion of the ballgroove nut 127 is shown abutting this spring 132. This view shows thebraking mechanism in the return position. This flange portion 135 isalso illustrated in PEG. 9 as a portion of the ball groove nut 127. PEG.11 also shows a portion of the annular hydraulic piston 125 which isconcentrically mounted around the shaft 121.

The attaching means for the cable are illustrated in FIG. 10. A portion136 of the ball groove nut 127 extends radially outward from the ballgroove nut. The cable 113s extends tangentially around the ball groovenut and through the portion 136 where it is attached to a ball 137 whichlocks the cable in position. As the outer portion of the cable ispulled, the ball 137 creates a pressure against the radial flange 13dand thereby rotates the ball groove nut 127.

This cable is also provided with a guide means on its outer end. Thisguide means is generally of the same structure previously described. Theball groove nut is shown rotatably mounted on the spherical balls 129.These balls are mounted on a helical mating groove on the internal ballgroove sleeve 123. The shaft 121 is shown concentrically mounted withinthe ball groove sleeve 128. The operation and assembly of this ballgroove sleeve is of the general structure previously described in thepreceding paragraphs of the other modifications.

The parking brake actuating mechanism operates in this manner: Referringto views 1 and 2, as the cable 53 is pulled outward for the actuation ofthe brakes, the ball groove nut 32 is rotated. The annular piston 25which is mounted concentrically within ball groove nut 32 has matingball grooves for receiving the spherical balls 61. As the ball groovenut is rotated in relation to the hydraulic piston 25, the hydraulicpiston moves axially inboard. This axially inboard movement of thehydraulic piston 25 continues until the flange portion 23a of the sleeve23 compresses the pressure plate 13 against the brake disk stack. As thebrake disks 9 and 1t) frictionally engage each other, the rotation ofthe vehicle wheel 1 is retarded.

The force on the flange 23a on the wheel piston 25 creates a reactionforce through the spherical balls 61 onto the ball groove nut 32. Thisforce is transmitted through the spherical balls 34 and transmitted tothe shaft housing 11.

This brake has the added feature of being assisted by the hydraulicsystem for actuating the brakes. This feature is an advantage in eventthat the brake disks are hot from constant use. The heat within thebraking structure causes an expension of the bra e disks which may causea release of the brakes if they are not actuated firmly. This brake,having a high mechanical advantage in the screw arrangement of the ballgroove nut, would not generally necessitate the use of the hydraulicfluid system, but in event that the operator should desire to use thisassisting force, the actuating of the wheel cylinder is in the samedirection in cooperation with the hand operating means.

The brake actuation by the foot pedal 31 displaces fluid within themaster cylinder 35M which creates a pressurized fluid within theactuating chamber of the housing ill and piston 25.

Upon release of the brakes either by the hydraulic actuating means orthe manual parking brake mechanism, the return spring tit returns thepiston 2.5 to its retracted position.

The brake actuating mechanism has a built-in clearance adjustment forthe brake disks. This adjustment is provided for in this manner: A screwmember 42 is mounted concentrically within sleeve member 45 on theradial flange of the housing member 11. These screws are angularlyspaced about the radial flange on a common radial circle of the housingmember 11. The sleeve member 45 is snugly fitted within the reamed holeof the hydraulic wheel piston 25. The screw 42 is screwed snugly againstthe flange portion of the housing member 11 with the shoulder 43abutting the flange portion of housing 11. The predetermined clearancewhich is to be provided between the brake disks is equal to thedifference in length of the distance from the shoulder portion &3 to thehead 44 of screw 42 and the length of sleeve 45.

As the hydraulic annular piston 25 is actuated, the piston 25 movesinboard carrying the sleeve t5. if excessive clearance exists betweenthe brake disks, the sleeve 45 will abut the head 44 and the head willslide sleeve 45 axially outboard in the annular hydraulic piston 25. Asthe brakes are released, the annular piston moves outboard carrying thesleeve 45 to a new position. The annular piston 25 does not completelyreturn to its original position, but only to the point where theoutboard edge of the sleeve 45 abuts the radial flange portion of thehousing 11. By this means, a constant clearance is provided between thebraking disks. This means that the annular cylinder will move a constantdistance for brake actuation whether it be by the hydraulic fluid systemor the parking brake actuation means.

The version illustrated in FIG. 7 operates in the same manner as theoriginal version of this brake actuating means, except the hydraulicwheel piston 191 and the ball groove nut 96 elongate, and the ballgroove nut forces against the annular member 99 into the spherical balls100. A torsion spring 51 is provided for returning the ball groove nutto its original position.

The modification illustrated in views 9, and 11 operates on the ballgroove principal with a ball groove nut and ball groove sleeve except aneedle hearing assembly 126 is placed between the ball groove nut 127and the hydraulic wheel piston 125. The return means for the parkingbrake actuating mechanism utilizes the compression coil spring insteadof the torsion-type spring, which is mounted concentrically around thewheel shaft.

While the embodiment of the present invention as herein disclosedconstitutes a preferred form, it is to be understood that other formsmight be adopted.

What is claimed is as follows:

1. A parking brake actuating mechanism comprising in combination, ahousing means, a shaft means rotatably mounted within said housingmeans, a wheel connected to said shaft means, stator disk meansconnected to said housing means, motor disc means connected with saidshaft means, an annular hydraulic cylinder means receiving annularpiston means for frictionally engaging said rotor disk means with saidstator disk means, a helical groove means on the outer periphery of saidannular piston, a nut having cooperating helical groove means andconcentrically mounted around the outer periphery of said annularpiston, means retaining said nut against axial movement relative to saidcylinder and piston, rolling elements received within said matinghelical groove means of said nut and said piston, a cable meansconnected to said nut for rotating said grooved nut relative to saidpiston and thereby axially moving said piston and compressing said diskmeans and actuating the braking means, an automatic clearance adjustmentmeans for said stator disk means and said rotor disk means and connectedto said housing member and including a sleeve member positioned in saidpiston and frictionally retained in said piston. a support member havinga shoulder for reception in said sleeve and having a head, said shoulderportion being of a predetermined length greater than said sleeve, themovement of said sleeve relative to said annular piston therebyproviding the adjustment for clearance between said stator disk meansand said rotor disk means.

2. A parking brake actuating means comprising in combination, a housingmeans, a shaft means rotatably mounted within said housing means, awheel member attached to said shaft means, one or more rotating disksattached to said shaft means, one or more stator disks attached to saidhousing means, an annular hydraulic wheel cylinder having an annularpiston therein for engaging said brake disks, a ball groove nutconcentrically mounted in said housing around the outer periphery ofsaid piston against axial movement relative to said piston, a helicalball groove on the outer periphery of said piston and a mating helicalball groove on the inner periphery of said ball nut for reception ofspherical balls for creating axial movement of said piston and actuationof said brake disks when said ball groove nut is rotated in relation tosaid piston, an automatic disk spacing means including screws mounted insaid housing means, a sleeve member carried on said screw member, saidsleeve member being of a predetermined shorter length than its mountingspace on said screw member, said sleeve member mounted Within a closefitted hole in said annular hydraulic wheel cylinder for movement ofsaid sleeve member in relation to said annular piston only when anexcessive clearance exists between said brakes, thereby providing aconstant clearance between said braking disks.

3. In a vehicle brake comprising, in combination, a stationary member,at least one stationary brake disc connected to said stationary member,a rotating member rotatably mounted on said stationary member, at leastone rotating brake disc mounted on said rotating member for frictionallyengaging said stationary member when the vehicle brakes are actuated,hydraulic means for actuating said vehicle brakes including a hydraulicwheel cylinder, a hydraulic wheel piston operating within said hydraulicwheel cylinder and forming an actuating chamber, an automatic clearanceadjusting means including a screw member threadedly engaging saidhydraulic cylinder, at head portion on said screw, a cylindrical portionadjacent said head of said screw member for reception of a sleeve, anopening in said hydraulic wheel piston for the reception of said headportion of said screw member and said sleeve, said sleeve fitting saidopening in said piston with a close tolerance to resist relativemovement to said hydraulic Wheel piston, said sleeve being of apredetermined shorter length than the cylindrical portion of said screwmember to control the clearance between the brake discs in theirretracted position, said head portion of said screw member shifting theposition of said sleeve relative to said piston during brake actuationto maintain the disk clearance.

4. In a vehicle brake comprising in combination, a stationary member, atleast one stationary brake disk connected to said stationary member, arotating member rotatably mounted on said stationary member, at leastone rotating brake disk mounted on said rotating member for frictionallyengaging said stationary brake disk when the vehicle brakes areactuated, a hydraulic wheel cylinder, a hydraulic wheel piston receivedin said hydraulic wheel cylinder and operating in cooperation with saidhydraulic wheel cylinder for actuation of said vehicle brakes, anautomatic clearance adjusting means including a scrca' member having athreaded portion threadedly engaging said hydraulic wheel cylinder, ahead portion on said screw member adjoined by a shank portion betweenthe threaded portion and said head portion or" said screw member, asleeve for receiving the shank portion of said screw met ber of apredetermined shorter length than a shank portion of said screw member,said sleeve and said head portion of said screw received within anopening in said hydraulic wheel piston, said sleeve constructed with aclose tolerance for frictionally engaging said opening in said hydraulicwheel piston to resist relative movement of said sleeve relative to saidhydraulic wheel piston, said head portion operating to move said sleeverelative to said piston when said vehicle brakes are actuated therebymaintaining a predetermined clearance between said brake discs in theirretracted position.

5. In a vehicle brake comprising in combination, a stationary member, atleast one stationary brake disc connected to said stationary member, arotating member rotatably mounted on said stationary member, at leastone rotating brake disc connected to said rotating member forfrictionally engaging said stationary brake disc when the vehicle brakesare actuated, a hydraulic wheel cylinder, a hydraulic wheel piston forreception within said hydraulic wheel cylinder, an automatic clearanceadjusting means including a screw member threadedly engaging saidhydraulic wheel cylinder, a head portion on said screw member adjoineclby a cylindrical shank portion, a sleeve loosely fitted about the outerperiphery of said shank portion of said screw member being of apredetermined shorter length than the shank portion of said screwmember, an opening in said hydraulic wheel piston for reception of saidscrew member and said sleeve member, said opening being of a closefitting tolerance relative to said sleeve member to provide a frictionalforce to resist relative movement of the sleeve relative to saidhydraulic wheel piston, the head portion of said screw member engagingthe end of said sleeve member to move said sleeve member relative tosaid hydraulic wheel piston when said vehicle brakes are actuated,thereby controlling the return position of said hydraulic wheel pistonrelative to said hydraulic wheel cylinder and providing an adjustmentfor maintaining a predetermined clearance between said brake discs whensaid vehicle brakes are in a retracted position.

6. In a vehicle brake comprising in combination, a stationary member, atleast one stationary brake disc connected to said stationary member, arotating member rotatably mounted on said stationary member, at leastone rotating brake disc mounted on said rotating member for frictionallyengaging the stationary brake disc when said vehicle brakes areactuated, a hydraulic wheel cylinder, a hydraulic wheel piston receivedwithin said hydraulic wheel cylinder and connected with a force applyingmember effecting actuating engagement of said brake discs, an auto maticclearance adjustment means including a stud member afiixed to saidstationary member, said stud member having a cylindrical shank portionextending from said stationary member and terminating in a head portion,a sleeve member loosely fitted about the outer periphery of saidcylindrical shank portion of said stud member and having a frictionalretaining fit in an opening in said force applying member, said sleevemember being of a predetermined shorter length than the shank portion ofsaid stud member controlling thereby the clearance between the brakediscs in their retracted position, said head portion of said stud memberengaging the end of said sleeve member to move said sleeve relative tosaid force applying member when said vehicle brakes are actuated formaintaining the clearance of said brake discs in the retracted position.

References Qited in the file of this patent UNITED STATES PATENTS2,619,198 Freund Nov. 25, 1952 2,866,526 Wiseman Dec. 30, 1958 2,937,723Hodkinson May 24, 1960

